Surgical microscopes provide a magnified view of the operating field to the surgeon. Ophthalmic surgical microscopes are commonly stereo zoom microscopes with binocular view ports for the surgeon, and frequently have one or two observer view ports at ninety degrees (left and right) to the surgeon. The working distance between the objective lens of the microscope and the surface of a patient eye may range from about 100 mm to about 200 mm. At this working distance, which provides a suitable field of access for the manual work of the surgeon, the field of view within a patient's eye may be quite limited. It is quite common to then use an intermediate lens, such as the Oculus BIOM—Binocular Indirect Ophthalmo Microscope, available from INNOVA Medical Ophthalmics of Toronto, Ontario, Canada, to modify the focal point, magnification, and field of view for the surgeon. This intermediate lens is mounted to the undercarriage of the microscope head, and includes mechanics to adjust focus and to flip the lens into and out of the field of view of the microscope.
Other illumination or imaging devices may also be used in the surgical field. All illumination and imaging sources often would desirably be directly integrated coaxial to, and within, the optical path of the operating microscope, without impacting the operating field for the surgeon, the observers, the anesthesiologists, and other operating room personnel. Such integration is not always possible. Without full integration as such, it may still be desirable to provide a readily maneuverable mount for imaging and other accessories that is closely coupled to the surgical field, and is compatible with the mechanical controls and attributes that are already helpful for providing a well-functioning operating microscope.
A particular case of interest is the incorporation of optical coherence tomography (OCT) imaging into the surgical visualization practice. OCT provides high resolution imaging of ocular tissue microstructure, and may be used to provide information to the surgeon that will improve therapeutic outcomes and reduce the total economic burdens of surgery by reducing risk and reducing rework. The current generation of OCT, known generally as Fourier Domain OCT, provides very fast volumetric images (>30 mega-voxels per second) at very high resolution (2.0 μm to 6.0 μm axial resolution, 10.0 μm to 20 μm lateral resolution). These OCT images may be helpful in visualizing the fine tissue layers and membranes that are often the subject of surgical effort. In contrast to microscope visualization, OCT provides depth-resolved images, highlighting subsurface physiology and pathology, with full volumes over a 30 to 70 degree field of view acquired in about 1 to 3 seconds. However, the alignment requirements of OCT, particularly for retina imaging and anterior segment imaging, may be quite demanding to obtain high quality images. A flexible, finely controlled, and stable imaging platform is desirable.
At present, there are no commercially available operating microscopes with integrated OCT capabilities. Handheld OCT devices are available to supplement the microscopes. However, in some embodiments, the handheld device may be relatively difficult to align and stabilize for imaging in the operating field.